MIDI music files can be played from the "sounds" subdirectory of the object path, in zip compressed format with a ".zip" file extension or from a URL file specification with a ".mid" extension.
MIDI music can be turned on or off in the General Settings dialog.
Legal
Before using any URL for sounds in your world, please make sure that using the specific URL for that purpose is not a violation of any contractual agreement or any law, including copyright laws.